b3GpuDynamicsWorld improvements:

apply forces
copy linear/angular velocity every frame at the CPU side, initial velocity works now
hook up setGravity
Note: the 'stepSimulation' for GPU only simulates a single simulation frame.

src/Bullet3OpenCL/RigidBody/b3GpuRigidBodyPipeline.h

@@ -33,7 +33,9 @@ public:
 	int		registerPhysicsInstance(float mass, const float* position, const float* orientation, int collisionShapeIndex, int userData, bool writeInstanceToGpu);
 	//if you passed "writeInstanceToGpu" false in the registerPhysicsInstance method (for performance) you need to call writeAllInstancesToGpu after all instances are registered
 	void	writeAllInstancesToGpu();
-
+	void	setGravity(const float* grav);
+	void reset();
+	
 	void	addConstraint(class b3TypedConstraint* constraint);
 
 	cl_mem	getBodyBuffer();